docker-util: Update the gcn-gpu docker image Cloud Bucket
docker-util: Update the gcn-gpu docker image Cloud Bucket

This is updated for the gem5 v21.1 release.

Change-Id: I84e663afdca41045a73e2fc25b87b53a6063202c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48663
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Bobby R. Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Maintainer: Bobby R. Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5